Energy consumption in wireless cellular systems can be handled in many ways:                By cell planning, deployment, antenna mast height, a large number of cells (and low power transmitters)        By directional antennas and antenna arrays        By energy efficient hardware design, e.g. for the power amplifier(s)        By low peak-to-average based modulation, efficient error correction coding, low overhead        By radio resource management (RRM) such as power control, rate control, scheduling, etc. However, traditionally RRM has focused on throughput related performance rather than efficient energy consumption issues. Typical examples are enhancement of system and/or individual user throughput, and fulfillment of certain Quality of Service requirements, such as minimizing delay.        
Reference [1] considers energy consumption for a packet over a single communication link, where the energy consumption is minimized by tuning transmit power and transmit rate.
Although many advances have been made to handle energy consumption issues in communication systems, there is still a general need for even more energy-efficient solutions to the resource management problem.